How Can I Prevent Null Values from Appearing in .NET XML Serialization?

Eliminating Null Values During .NET XML Serialization

The default behavior of .NET's XmlSerializer includes null values in the serialized XML output. This can often be undesirable. Let's examine how to prevent this. Consider the following XML generated from a sample class:

<code class="language-xml"><?xml version="1.0" encoding="utf-8"?><myclass><mynullableint p2:nil="true" xmlns:p2="http://www.w3.org/2001/XMLSchema-instance"></mynullableint><myotherint>-1</myotherint></myclass></code>

Notice that mynullableint, a nullable integer set to null, is still present in the XML. The solution lies in using the ShouldSerialize pattern.

To exclude a null MyNullableInt property, implement this method within your class:

<code class="language-csharp">public bool ShouldSerializeMyNullableInt()
{
  return MyNullableInt.HasValue;
}</code>

This method conditionally controls serialization. It returns true only if MyNullableInt holds a value, ensuring its inclusion in the XML. Otherwise, it returns false, effectively suppressing the element.

Here's a complete example:

<code class="language-csharp">public class Person
{
  public string Name { get; set; }
  public int? Age { get; set; }
  public bool ShouldSerializeAge()
  {
    return Age.HasValue;
  }
}</code>

With this ShouldSerializeAge method, the following code produces XML without the Age element because it's null:

<code class="language-csharp">Person thePerson = new Person() { Name = "Chris" };
XmlSerializer xs = new XmlSerializer(typeof(Person));
StringWriter sw = new StringWriter();
xs.Serialize(sw, thePerson);</code>

Resulting XML:

<code class="language-xml"><person xmlns:xsd="http://www.w3.org/2001/XMLSchema" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"><name>Chris</name></person></code>

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